The present invention relates to a temperature sensor, and more particularly to a Michelson interferometer temperature sensor by combining a silicon-on-insulator waveguide coupler with two silicon-on-insulator waveguide Bragg gratings.
According to the present developments of the optical sensor, the fiber Bragg grating is still one of the major components for providing physical measurements. But the manufacturing time of the fiber Bragg grating is longer than that of the semiconductor grating, and the yield thereof is less than that obtained using semiconductor techniques. In addition, the size of the fiber Bragg grating is larger than that of the semiconductor waveguide, and thus the cost cannot be reduced.
Since the optical fiber communication network develops very fast, each reliable subscriber needs many highly accurate optical sensors built in key components. Developing low cost optical waveguide sensors based on the semiconductor manufacturing process will therefore be a trend in related fields.
Silicon is very easy to acquire and very cheap, and has been the major material in the IC manufacturing process, so the present invention uses silicon-on-insulator as the substrate. The advantages of high bandwidth and low power loss of MOSFET based on silicon-on-insulator lead it to be the best choice for the future OEIC (Optoelectronic Integrated Circuit).
The present invention applies the technology of IC semicoductor manufacturing process to the field of optical sensor to reduce the size of the component significantly.
A. D. Kersey and T. A. Berkoff disclosed in IEEE Photonics Technology Letters, vol. 4, no. 10, 1992, page 1183xcx9c1185 that the fiber Bragg grating was used as a temperature sensing component, having an accuracy of 0.05xc2x0 C. That result proved the feasibility of using Bragg grating as a temperature sensor. But the manufacturing cost is too high, and the effect is not so good as the temperature sensor of the present invention designed by using silicon-on-insulator waveguide grating.
Wei-Chong Du, Xiao-Ming Tao and Hwa-Yaw Tam disclosed in IEEE Photonics Technology, vol. 11, no. 1, 1999, page 105xcx9c107 that the reflective spectrum of the fiber Bragg grating was used to analyze the variation of the temperature. However, the present invention uses two reflective gratings and Michelson interferometer effect to reduce reflective spectrum linewidth and achieve a more accurate temperature monitoring.
A. D. Kersey and T. A. Berkoff disclosed in IEEE Photonics Technology Letters, vol. 8, no. 9, 1996, page 1223-1225 that the fiber Bragg grating was successfully used as a temperature and pressure sensor, but the cost can""t be reduced. The present invention utilizes the semiconductor technology to lower the cost.
T. W. Ang, G. T. Reed, A. Vonsovici, A. G. R. Evans, P. R. Routley and M. R. Josey disclosed in IEEE Photonics Technology Letters, vol 12, no. 1, 2000, page 59xcx9c61 that the effect of the silicon-on-insulator waveguide grating was analyzed, and proved the feasibility of the silicon-on-insulator waveguide grating sensor.
Eric Udd disclosed in U.S. Pat. No. 5,591,965 (1997) that a sensor system was designed by a plurality of fiber gratings, and therefore proved the feasibility of multiplex physical measurement by fiber grating. However, the present invention does not use the periodic fiber grating shown in U.S. Pat. No. 5,591,965, but rather utilizes a semiconductor manufacturing process for commercialization.
Mark F. Krol disclosed in U.S. Pat. No. 96,075,907 (2000) that a plurality of fiber gratings of long period were arranged in a fiber network for monitoring the physical quantities of many points, such as temperature . . . and so on. U.S. Pat. No. 96,075,907 proved that an optical temperature sensor is very useful in fiber network, but the technology thereof is different from the present invention.
Stephen James Crampton, Arnold Peter Rosc and Andrew George Rickman disclosed in U.S. Pat. No. 5,757,986 (1998) that an optical modulating component was designed using a silicon-on-insulator waveguide, proving that the silicon-on-insulator waveguide is very useful and marketable.
The present invention provides a Michelson interferometer temperature sensor including a 2xc3x972 waveguide coupler and two waveguide Bragg gratings based on silicon-on-insulator substrate. The temperature can be read out through the sensor. The temperature variation can induce the wavelength response variation which results in the power variation. Since the thermal-optical expansion coefficient of the silicon-on-insulator is higher than that of a fiber, it can enhance the reslution of temperture measurement significantly.